1. Field of the Invention
The present invention relates generally to the field of electrical component panels and techniques for interconnecting power and data conductors in such panels. More particularly, the invention relates to a technique for providing multiple plug-in connections in a panel or cabinet structure through a wiring topography which can be readily and economically installed to provide a highly flexible and reliable device infrastructure.
2. Description of the Related Art
A wide range of electrical devices are assembled and interconnected in panels, cabinetry, enclosures, and the like. Traditionally, switch gear has been mounted on panels within enclosures and interconnected via individual wires run between terminals of each switch gear component. Troughs or conduits may be provided between the components to protect the wires and to facilitate both installation and servicing. Where electrical power and data signals are exchanged between external circuitry and the enclosed components, separate conductors have commonly been routed, with power conductors often separated physically within the enclosures to avoid potential for interference and short circuits, and to conform to industry standards and codes.
In a special type of electrical component assembly, commonly referred to as a motor control center or MCC, three phase power and data signals are exchanged between panel-mounted components and external circuitry. In this exemplary application, special wireways are provided for routing wiring separate from regions in which the components are mounted. Where low-level power is provided for sensors, controllers, actuators, and the like, these are sometimes grouped in twisted conductor sets with data conductors. In such cases, all power and data conductors are individually terminated at both ends to wire the components to one another and to the external circuitry. Where an industrial control network is employed to interface with the components, the wiring topography may provide for xe2x80x9cdaisy chainingxe2x80x9d the components to one another in a series fashion. Higher power electrical supply is routed separately, with power conductors being fed through power buses, typically three-phase buses, and connected to line-side terminals of relays, switches, contactors, and the like.
A number of drawbacks exist in conventional wiring topographies of the type described above and the resulting systems. For example, where wires are individually terminated, they must generally be stripped and installed in a time-consuming process. Where multiple power and data conductors are provided in a cable assembly, such assemblies are often shielded, requiring the removal of a portion of the shield prior to termination of the individual conductors. In systems where insulation-piercing components are used to facilitate termination, the conductors may still require shielding to be removed and individual conductors to be laid out in a desired manner in the connectors.
Additional drawbacks result from the topography adopted in conventional conductor-terminated systems. For example, where components are individually wired and xe2x80x9cdaisy chainedxe2x80x9d to one another, removal of an upstream component, such as for servicing, can result in the need to temporarily disconnect all downstream components. Depending upon the application, therefore, down time of the downstream components, as well as other components in the system can result. In extreme cases, removal of a component can require interruption of entire operations or processes.
Heretofore known wiring techniques and topographies also pose difficulties when used in conjunction with higher power circuits in a single enclosure or panel. For example, industry standards may require specific physical spacing between higher voltage power conductors and lower voltage instrumentation lines. Where wireways in the component enclosures do not offer such separation, arrangements must be made to accommodate the conductors and to maintain the desired separation. Again, this can imply a relatively time-consuming operation that affects the overall cost of the system, both upon installation and during later servicing.
There is a need, therefore, for an improved technique for interconnecting components in electrical systems, such as MCC""s and the like. There is, in particular, a present need for a wiring topography which is relatively time-efficient to install and service, and which offers flexibility in interfacing with a wide range of components, as well as in removal of components during servicing with a minimal amount of disruption to other components and systems.
The present invention provides a wiring topography technique designed to respond to these needs. The technique may be employed in a wide range of systems, particularly in systems in which a number of electrical components are coupled to power and data conductors for remote control and monitoring operations. The technique is particularly well suited to MCC""s and similar panel-mounted systems in which both higher power conductors and instrumentation-level conductors are routed in wireways or on the surface of support panels for feeding power and command signals to components and for retrieving feedback signals via data conductors.
The inventive topography is based upon provision of primary or trunk conductors in a first routing level, and drop or tap conductors in a second level. The trunk conductors are preferably provided in a flat cable which can be installed with mating connectors via insulation-piercing conductive elements. The drop conductors may be provided in similar flat cable which is interfaced with the trunk cable to feed a number of locations within the system. The drop cables may be installed in wireways which meet a wireway of the trunk cable to provide a clean and straightforward infrastructure during installation and later servicing. Connectors on the drop cable may also be installed via insulation-piercing conductive elements. The connectors on the drop cables facilitate interfacing with components via plug-in sockets.
The basic infrastructure established by the wiring topography may be installed during initial configuration of the system. In a preferred embodiment, the trunk and drop cables are pre-installed in corresponding wireways, with sockets being exposed for receiving plugs directly to the mounted components. The components may be separately mounted, such as on removable panels, or directly installed in the enclosure on fixed supports. The components may then be interfaced with the drop and trunk cable conductors via plugs. For later servicing, individual components can be unplugged and removed or replaced without interrupting service to upstream or downstream components, or to the drop or trunk cables.